The present invention relates to a Pegasus-type data cartridge which is capable of high-density recording (back memory) of e.g. CPU data.
The Pegasus-type data cartridge is disclosed in, for example, Japanese Patent Application H2-400760 filed by the present applicants.
In this type of Pegasus data cartridge, as shown in FIGS. 3, 4 and 6, a cartridge 1 is formed by attaching, with screws or the like, a thin box shaped upper cover 3 formed of a transparent synthetic resin to a top of a metal base plate 2 made of aluminum or the like. In addition, the cartridge 1 has a small width section 1A having a smaller width W1 in the transverse direction in FIG. 3, and a large width section 1B having a larger width W2, which are integrally formed and are symmetrical in the transverse direction with respect to a cartridge center line P1.
A pair of left and right tape reels 4 are rotatably supported in the large space in the large width section 1B so as to be symmetrical in the transverse direction with respect to the cartridge center line P1. A magnetic tape 5 wound around the pair of tape reels 4 is guided by a pair of left and right tape guides 6 and 7 which are attached to be symmetrical relative to the cartridge center line P1 in the small width section 1A, and is conveyed in an inverted squared U shape along a front face la of the small width section 1A.
A drive roller 8 is rotatably supported in the small width section 1A of the cartridge 1 on the cartridge center line P1 and on the inside of the magnetic tape 5, and a pair of left and right corner rollers 9 are rotatably supported in identical left and right corner sections toward a rear face 1b of the large width section 1B opposite the small width section 1A to be symmetrical relative to the cartridge center line P1.
A drive belt 10 made of rubber or the like with elasticity is wound at a high tension in an inverted T-shape around and between the drive belt 8 and both corner rollers 9. A pair of left and right drive sections 10a of the drive belt 10 between the drive roller and the corner rollers 9 are wound around the outer circumferences of both tape reels 4 and are brought into pressure contact with the outer circumferences of tape winding sections 5a of the magnetic tape 5.
A notch 11 is formed in the base plate 2 and the upper cover 3 at the front face la of the small width section 1A. Also, the tape reels 4, the tape guides 6, the drive roller 8 and the corner rollers 9 etc. are rotatably supported through their center holes 13 on metal support shafts 12 implanted in the base plate 2.
As shown in FIG. 1(B), both corner rollers 9 (as well as the drive roller 8) are made of synthetic resin such as polyacetal resin or the like, an integrated belt-winding surface 14 is formed on the outer circumferences of these rollers, and torque control grease 15 is filled into the center holes 13 thereof.
With this type of Pegasus data cartridge, the small width section 1A of the cartridge 1 is inserted in the direction of an arrow a (see FIG. 4) into a cartridge insertion slot 22 formed in the front panel of the record/playback device 21. Then, an output roller 24 and magnetic head 25, which are rubber rollers drivingly rotated by a spindle motor 23 inside the recording/playback device, are reciprocatingly inserted into the notch 11 of the cartridge 1, so that the output roller 24 and magnetic head 25 press and contact against the drive roller 8 and the magnetic tape 5.
Accordingly, in the installed state of the cartridge 1 in the recording/playback device 21, the large width portion 1B projects in a transversely symmetrical state from the cartridge insertion slot 22.
With the thus installed cartridge, according to an instruction signal from a CPU, the drive roller 8 is drivingly rotated in a direction of an arrow b (see FIG. 3) and the drive belt 10 is driven in the direction of an arrow c by the output roller 24, both tape reels 4 are drivingly rotated in a direction of an arrows d by the drive sections 10a of the drive belt 10 via the tape winding sections 5a, and the magnetic tape 5 advances at a high speed of 25 to 120 inches/sec. in a direction of an arrow e. The data of the CPU are recorded on or played back from the magnetic tape 5 by the magnetic head 25.
Additionally, since this type of Pegasus data cartridge, in the state where it is installed in the recording/playback device 21, has the large width section 1B projecting outside the cartridge insertion slot 22 and the pair of tape reels 4 rotatably received in the large space inside the large width section 1B, can house the magnetic tape 3 having a sufficiently large diameter on the tape reels 4 to record a large volume of data from the CPU.
When an eject button 26 provided in the front panel 21a is pushed by the user's finger, this cancels the lock of the small diameter section 1A inside the cartridge insertion slot 22 and the cartridge 1 can be ejected from the cartridge insertion slot 22 in a direction of an arrow f.
However, in a Pegasus data cartridge of this type, a speed difference occurs between the drive sections 10a of the drive belt 10 due to the rotation load imposed on the corner rollers 9, and there is a fixed tension and tape drive force between the two tape reels 4 for holding the magnetic tape 5. Consequently, if variations in the tape tension and tape drive force are increased, there are problems of inadequate contact between the magnetic tape 5 and the magnetic head 25, insufficient tape advance of the magnetic tape 5, and considerable deterioration of recording and playback accuracy.
On the other hand, this type of Pegasus data cartridge differs from a standard mini-data cartridge in which the entire cartridge 1 can be placed completely inside, and the passages of the magnetic tape 5 between the two tape reels 4 and the drive belt 10 between the drive roller 8 and the two corner rollers 9 are both extremely long. Additionally, the tape drive speeds difference according to CPUs of each maker: for example, since the range of 25 to 120 inch/sec. is extremely wide, it is very difficult to stabilize the tape tension and tape drive force for each tape drive speed.
As of the present, the Pegasus-type data cartridge of the prior art example has been utilizing the corner rollers of the standard mini cartridge as they are, for its corner rollers 9.
In other words, in the Pegasus-type data cartridge of the prior art example, as shown in FIG. 1(B), the outer diameter A1, which is the maximum diameter of the belt-winding surface 14 of the corner rollers 9, is 10.86 mm, the measurement of the inner diameter B1 which is the diameter of the center hole 13 is 3.22 mm, and the ratio of the inner diameter B1 to the outer diameter A1 is A1/B1=approx. 3.37.
However, in the prior art Pegasus-type data cartridge, since the outer diameter A1 of the corner rollers 9 is small, when the magnetic tape 5 is advanced, the rotation speed of the corner rollers 9 is high, friction loss at the corner rollers 9 is high, and the rotational load thereof is high. Friction loss is determined by moment relationship, and is proportional to the B1/A1.
Accordingly, the prior art Pegasus-type data cartridge is prone to fluctuations in the magnetic tape 5 and the drive belt 9 due to the large rotational load on the corner rollers 9 as well as the length of the passages of the magnetic tape 5 and the drive belt 10, as described above.
In FIGS. 5(A) and (B) are graphs showing measurements of the tape tensions and tape drive forces of the magnetic tape 5 of the prior art Pegasus-type data cartridge having corner rollers 9 with outer diameters A1 of 10.86 mm and inner diameters B1 of 3.22 mm, at the three tape drive speeds of 30 inch/sec., 80 inch/sec., and 120 inch/sec. The ideal upper limit value of the tape tension shown in FIG. 5(A), is approx. 108 g, while the ideal lower limit value thereof is approx. 17 g, and the ideal upper limit value of the tape drive force shown in FIG. 5(B) is approx. 128 g, while the ideal lower limit value is approx. 27 g.
As is clear from this graph, in the prior art Pegasus data cartridge, as the tape drive speed increases, there is more tendency for fluctuations to occur in the magnetic tape 5 and the drive belt 10 and the characteristic values of the tape tension and the tape drive force both rise considerably, the tape tension and tape drive force both departing greatly from their ideal upper limit values. Consequently, as the tape drive speed increases, the problems of contact deterioration occurring between the magnetic tape 5 and the magnetic head 25, deterioration of the tape advance of the magnetic tape, and significant distortion of recording and playback precision arise.
As a method for reducing the tape tension and the tape drive force, there is a method of reducing the elasticity of the drive belt 10, but as the elasticity of the drive belt 10 is reduced, winding perturbation of the magnetic tape 5 tends to occur with respect to the tape reels 4, and off-track problems occur with the magnetic head 25, therefore this solution is unacceptable.
Also, in the data cartridge of the prior art Pegasus-type, as shown by the one-dotted lines in FIG. 3, a pair of left and right connecting surfaces 1e connecting the left and right side surfaces 1c and 1d of the small width section 1A and large width section 1B of the cartridge 1 is formed parallel to the front panel 21a of the recording/playback device 21.
Consequently, in the state where the cartridge 1 is installed, with the small width section 1A of the cartridge 1 inserted in cartridge insertion slot 22 of the recording/playback device 21, one of the connecting surfaces 1e of the cartridge 1 is located very close to the eject button 26 provided in the front panel 21a, and since the gap G1 between the two is extremely small, there is the problem that it is very difficult for the operator to operate the eject button 26 with his/her finger.
The present invention has been arrived at in order to solve the above two problems, and its object is to provide a Pegasus-type data cartridge which can suppress an increase in the characteristic values of the tape tension and tape drive force even when the tape drive speed is increased, and in which the eject button can be easily operated in the state where the cartridge is installed in a recording/playback device.